This invention is directed to organosilicon aldehydes and ketones, methods for their preparation, and more particularly to multi-functional carbonyl functional silanes.
There have been previous attempts to prepare silanes having multi-functional moieties attached to the silicon atom. For example, silanes having non-labile (stable) groups such as alkyl and aryl, together with labile (unstable) aldehyde and ketone groups, are known in the art, as evidenced by U.S. Pat. No. 3,344,104 (Sep. 26, 1967).
However, there is continuing interest in manufacturing other types of multi-functional silanes having several different labile groups attached to the same silicon atom. Such multi-functional silanes can be used in various reactions corresponding to the labile functional groups.
Previous attempts to prepare silanes having another labile group on the same silicon atom have not been successful, however. For example, an attempted addition of methyldiethoxysilane or methyldichlorosilane to acrolein CH.sub.2 .dbd.CH--CH.dbd.O gave only an intractable mixture, Journal of the American Chemical Society, Volume 79, Pages 3073-3077, Jun. 25, 1957. Therefore, ozonolysis of silanes containing unsaturation has been developed by the present inventors as a viable alternative procedure.
In this regard, the reaction of ozone (O.sub.3) with a carbon-carbon double bond is known. Historically, however, the reaction has only been used as an analytical method to determine the position of a double bond along a hydrocarbon chain. Based on early studies and published reports, it is generally agreed among artisans that an ozonide intermediate is formed upon exposure of the double bond to ozone.
Thus, ozonolysis of alkenes leads to formation of an ozonide intermediate. The ozonide intermediate is a five-member peroxy-ether ring shown below: ##STR1## in which R1, R2, R3, and R4, are hydrogen, an alkyl group such as methyl, or an aryl group such as phenyl. When R1, R2, R3, and R4, are each hydrogen, for example, the ozonide is 1,2,4-trioxolane. When R.sub.1 and R3 are hydrogen, and R2 and R4 are methyl, for example, the ozonide is 3,5-dimethyl-1,2,4-trioxolane.
These ozonide intermediates are not stable, however, and readily rearrange to various hydroperoxides, dimeric and polymeric peroxides, and other oxygen containing compounds. According to the literature, it is generally agreed among artisans that in most cases, these ozonides break down rapidly, and initially form more stable zwitterion intermediates.
But under suitable conditions, a clean and efficient reaction can be attained, and an ozonide can be converted to an organic aldehyde using an appropriate reducing agent and reaction temperature. The solvent plays an important role in the stabilization of ozonide intermediates and their reduction to organic aldehydes. The choice of solvent depends upon the particular alkene being used, and some solvents are more efficient than others.
Thus, some preferred solvents are aprotic solvents such as carbon tetrachloride, methylene chloride CH.sub.2 Cl.sub.2, and chloroform CHCl.sub.3, which lead to high yields of ozonides, which can then be reduced subsequently to organic aldehydes or ketones.
Typical of reducing agents that have been employed in such organic syntheses include sodium iodide in the presence of water, potassium iodide in the presence of water, sodium iodide in the presence of acetic acid, potassium iodide in the presence of acetic acid, zinc in the presence of water, magnesium in the presence of water, zinc in the presence of acetic acid, and magnesium in the presence of acetic acid.
Examples of other reducing agents that can be used in preparing organic aldehydes or ketones from ozonide intermediates are sodium bisulfite NaHSO.sub.3, ferrous sulfate FeSO.sub.4, potassium ferrocyanide K.sub.4 Fe(CN).sub.6 !, stannous chloride SnCl.sub.2 in the presence of hydrochloric acid, tin in the presence of hydrochloric acid, ferrous ammonium sulfate (NH.sub.4).sub.2 Fe(SO.sub.4).sub.2, silver nitrate AgNO.sub.3, trimethyl phosphite (CH.sub.3 O).sub.3 P, quinol (hydroquinone) C.sub.6 H.sub.4 (OH).sub.2, pyridine N(CH).sub.4 CH, piperidine C.sub.5 H.sub.11 N, sulfur dioxide, and dimethyl sulfide (CH.sub.3).sub.2 S.
Despite the fact that such information is available to artisans on converting organic compounds containing unsaturated carbon-carbon double bonds to organic carbonyl compounds by ozonolysis and reduction, the ozonolysis and reduction procedure has not been applied in the conversion of silanes having carbon-carbon double bonds to silicon-containing carbonyl compounds.
In fact, only relatively few procedures have been successful in preparing multi-functional silanes, including for example, the UV irradiation of vinylsilanes in the presence of an organic aldehyde yielding a silicon-containing ketone, Bulletin of the Academy of Sciences, USSR Division of Chemical Science, Number 8, Pages 1405-1407, (August 1966); and the reaction of silicon-containing nitriles with a methyl Grignard reagent yielding a silicon-containing ketone, in the Journal of General Chemistry of the USSR, Volume 38, Number 2, Pages 380-385, February 1968.
Yet such procedures have not been useful commercially, either because of poor yield, the occurrence of extensive side reactions, or significant costs associated with starting materials or the process itself. Our invention resolves these problems, and provides an efficient method of obtaining multi-functional silanes containing the carbonyl group.